The present invention relates to a projection image display apparatus for projecting an image onto a projection surface using an image display element such as a liquid crystal panel, a screen of the projection surface, and a manufacturing method thereof, in particular, the present invention relates to technology to make a projection apparatus obtained by combination thereof more compact and higher performance.
For example, in the projection image display apparatus for displaying in an enlarging way a display screen of a reflection type or transparent type liquid crystal panel, or an image display element with a structure arranged with a plurality pieces of micro mirrors, onto a screen or a board etc. of the projection surface, it is needless to say that a sufficiently enlarged image is designed to be obtained on the projection surface. However, what is called a short-projection-type projection optical system has begun appearing on the market, which has shortened distance between the projection image display apparatus and the projection surface, so that a shadow of a presenter is not reflected onto the projection surface or an enlarged image light does not directly enter the eyes of the presenter. This projection optical system is configured so that the enlarged image light enters from an oblique direction relative to the projection surface (for example, JP-A-2008-250296).
In addition, it has also been known means for performing optical adjustment in an oblique projection optical system using a curved mirror for such oblique projection (for example, JP-A-2002-350774).
Still more, it has also been known the projection image display apparatus for attaining an ultra-thin-type compact rear-projection-type apparatus (image display apparatus), using this oblique projection optical system and a mirror for folding light path, so that a shadow of a presenter is not reflected onto the projection surface, or an enlarged image light does not directly enter the eyes of the presenter (for example, JP-A-2006-259252).
As a transparent screen optimal to this projection image display apparatus, conventionally, there has been generally a two-piece constitution screen composed of a diffusion sheet 170 (Also, lenticular sheet is possible) made of a diffusion layer 171 and a diffusion sheet substrate 172, as image light R1 and R2 in FIG. 37 and FIG. 38, and a circular Fresnel sheet 167 arranged with a circular Fresnel surface at a view side. Application of this transparent screen to the oblique projection optical system, as illustrated in FIG. 38, does not provide sufficient refraction of image light R1 and R2, and the image light R1 and R2 enters onto the diffusion sheet 170 from an oblique direction, so that a peak brightness direction is not only unable to be controlled to a desired direction but also it generates large reflection loss. Accordingly, there has been proposed a screen with a two-piece constitution by the diffusion sheet 170, as illustrated in FIG. 39 and FIG. 40, and a circular Fresnel sheet 166 of a total reflection system having a Fresnel lens surface oriented toward the side of the projection image display apparatus. As a result, there has also been known already a system which is capable of largely reducing reflection loss, even in corresponding to the oblique projection optical system (for example, JP-A-4-80369).
Still more, there has also been proposed already an image projection system with enhanced convenience by integrating the projection image display apparatus using a general projection optical system, and a reflection type screen (for example, JP-3864051, WO 00/52526).